The federal response to a ruinous storm in Puerto Rico began to take shape Monday as the scope of devastation on the US territory came into view. Top aides to President Donald Trump, including homeland security adviser Tom Bossert and the Federal Emergency Management Agency administrator Brock Long, touched down on the island Monday to assess immediate needs. Navy and Marine Corps teams were deployed to Puerto Rico to assist in recovery efforts. And lawmakers and the White House began to contemplate the enormous amount of federal dollars that will eventually be required to rebuild parts of the island. Trump himself has vowed to travel to Puerto Rico, as he did in the immediate aftermath of storms in Texas and Florida, but officials say the devastated territory is not yet capable of hosting a presidential visit. He hasn’t made mention of the shattered island on his Twitter feed or in public remarks over the past several days. At the White House, aides were working to prepare a disaster relief request to Congress. Republican leaders on Capitol Hill, as well as the chairs of the spending panels that would craft such a disaster funding package, have not yet received any specific requests from the Trump administration for how much money Puerto Rico will need. As of Monday morning, FEMA had $5.03 billion available for disaster spending between now and the end of September, an agency spokesperson told CNN. When the new federal fiscal year begins on October 1, the disaster relief fund will be replenished with an additional $6.7 billion. The spokesperson said the agency “anticipates a supplemental funding request in the near future.” White House press secretary Sarah Sanders said it was too early to identify a spending amount to request from Congress given the still-fresh destruction. “Once we have a greater insight into the full assessment of damage then we’ll be able to determine what additional funds are needed,” she said. Defending the federal response in Puerto Rico, Sanders said the White House’s reaction had been “anything but slow.” “In fact, there’s been an unprecedented push-through of billions of dollars of federal assistance that the administration has fought for,” she said. Speaking on CNN Monday, Puerto Rico Gov. Ricardo Rossello said any aid package must be commensurate with the scale of his island’s devastation. “We need to prevent a humanitarian crisis occurring in America. Puerto Rico is part of the United States. We need to take swift action,” he said. He warned of a “massive exodus to the United States” should the island be unable to recover. Puerto Ricans are American citizens and face no barriers to entering the United States. Many of the needs in the islands are still unknown, complicating efforts to assign federal aid dollars. Many areas of Puerto Rico are still inaccessible, and communications and power systems are mostly still out across the island. The aging infrastructure there, which was already in need of repair before the back-to-back storms hit, is also hampering efforts to gauge the damage. People attempting to travel to areas to make phone calls or get help or medicine are having trouble getting around, people familiar with the federal response said, with some bridges and main roads impassable. FEMA is helping to deliver emergency fuel to hospitals, which are struggling to keep up with demands. A request for emergency funding would require approval from Congress. House Speaker Paul Ryan issued a statement on Monday stressing that he stands ready to act. “Congress is working with the administration to ensure necessary resources get to the US territory. Our fellow citizens in Puerto Rico remain in our prayers as we make sure they have what they need,” the Wisconsin Republican said. The speaker recently visited Florida and Texas to survey storm damage in those states still recovering from Hurricanes Irma and Harvey, but he is unlikely to travel to the Puerto Rico while the island is still dealing with restoring basic power and communications capabilities. At an event in Texas last week Ryan mentioned Puerto Rico as one of the places they are still working to assess the recovery needs, and vowed that Congress would take up two disaster bills in October. Two senior House GOP sources tell CNN they expect to get the official request from the Trump administration in mid-October. As some Democrats are beginning to publicly worry that Puerto Rico is not getting the same amount of swift attention that Florida and Texas received after recent hurricanes caused record flooding and power outages, the top Republican who is working on the aid package made a point to say they will get the same help as others. “The people of Puerto Rico and the US Virgin Islands remain in our thoughts as they struggle to recover from successive Hurricanes Irma and Maria. The challenges they face are truly tremendous. But they should be reassured that they are entitled to equal treatment under the law and the Appropriations Committee and House leadership will assure that every step of the way,” House Appropriations Committee Chairman Rodney Frelinghuysen said. New York Democratic Rep. Jose Serrano sent a letter to the President on Friday calling for the creation of a joint task force made up of federal, local, and congressional leaders that is similar to the one set up after Superstorm Sandy damaged New York and New Jersey. “Due to the magnitude of destruction brought by Hurricane Maria, we believe that a long-term comprehensive and collaborative framework is necessary in order to rebuild Puerto Rico, its economy, its health care system and its infrastructure,” Serrano wrote. An aide familiar with the discussions tells CNN that the administration is reviewing the request for a task force. Florida GOP Sen. Marco Rubio visited Puerto Rico on Monday, and he penned a letter with his Democratic counterpart, Sen. Bill Nelson, to urge full federal support for Puerto Rico and the US Virgin Islands.